We immediately began an investigation into these unusual kills, and we detected a group of new accounts using an exploit to cast an internal spell to kill Mythic raid bosses, including Chrome King Gallywix.
Our security engineers quickly moved to put a stop to the cheat and take action against the accounts involved, and we have cleared the Hall of Fame to await the rightful winner of the RWF.
Thank you to everyone who reported this. We will continue to employ the utmost vigilance about fair play in World of Warcraft.